1. Field of the Invention
The present invention relates to a temperature measuring apparatus and a temperature measuring method.
2. Description of the Related Art
Accurately measuring a temperature of a substrate, for example, a semiconductor wafer or a liquid crystal display (LCD) substrate, to be processed by using a plasma processing apparatus is very important in order to accurately control shapes, properties, and so on of films or holes formed on or in the semiconductor wafer or the LCD substrate based on the result of various processes such as film formation and etching. Accordingly, a temperature of a semiconductor wafer or a LCD substrate has been measured by using various conventional methods such as a temperature measuring method using a fluorescent thermometer for measuring a temperature of a rear surface of a substrate, a resistance thermometer, or the like.
Recently, a temperature measuring technology using a low-coherence interferometer which can directly measure a temperature of a substrate, which is difficult to do with the conventional temperature measuring methods, has been developed. Also, as the temperature measuring technology using the low-coherence interferometer, a technology has been suggested in which a light from a light source is divided into a measurement light for temperature measurement and a reference light by a first splitter, the measurement light is divided into n measurement lights by a second splitter, the n measurement lights are emitted to n measurement points, and interference between reflected lights of the n measurement lights and a reflected light of the reference light reflected by a reference light reflecting unit is measured to simultaneously measure temperatures of the plurality of measurement points (refer to, for example, Patent Reference 1). According to such a technology, temperatures of a plurality of measurement points may be simultaneously measured with a simple structure. Also, a temperature measuring technology using a low-coherence interferometer, which can convert measurement lights by a multiplexer and supply the converted measurement lights to a plurality of processing chambers to measure temperatures of substrates or the like inside the processing chambers, has been developed (refer to, for example, Patent Reference 2).
In the temperature measuring technology in which the measurement lights are converted by the multiplexer and supplied to the plurality of processing chambers to measure the temperatures of the substrates or the like inside the processing chambers, since the measurement lights are converted by the multiplexer and supplied to the plurality of processing chambers, the temperatures of the substrates or the like inside the processing chambers cannot be simultaneously measured.    [Patent Reference 1] Japanese Laid-Open Patent Publication No. 2006-112826    [Patent Reference 2] Japanese Laid-Open Patent Publication No. 2008-216182